Solving Equations with 2 Variables

The cost of $x$ snacks is $2x$, and the cost of $y$ waters is $y$. The total amount is 20, so the equation is $2x+y=20$.

The cost of $x$ apples is $3x$, and the cost of $y$ oranges is $2y$. The total amount is 30, so the equation is $3x+2y=30$.

The equation formed here is $2x+3y=40$, where $x$ is the number of pencils and $y$ is the number of erasers. Buying 5 pencils gives us $2(5)+3y=40$. Solving this, we find $y=10$. So, you can still afford 10 erasers.

The equation formed here is $2x+3y=40$, where $x$ is the number of pencils and $y$ is the number of erasers. Buying 8 erasers gives us $2x+3(8)=40$, which simplifies to $2x+24=40$. Solving this, we find $x=8$. So, you can still afford 8 pencils.

The equation formed here is $2x+3y=40$, where $x$ is the number of pencils and $y$ is the number of erasers. Buying 6 pencils and 3 erasers gives us $2(6)+3(3)=12+9=21$. So, you've spent 21. Subtracting this from your total, $40-21=19$, meaning you have 19 left.

The equation represented is $2x+3y=40$, where $x$ is the number of pencils and $y$ is the number of erasers. Point $P$ shows $x=5$ and $y=10$, meaning 5 pencils and 10 erasers can be purchased.